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Deeply Subwavelength Metasurface Resonators for Terahertz Wavefront Manipulation
Author(s) -
Liu Mingkai,
Yang Quanlong,
Rifat Ahmmed A.,
Raj Vidur,
Komar Andrei,
Han Jiaguang,
Rahmani Mohsen,
Hattori Haroldo T.,
Neshev Dragomir,
Powell David A.,
Shadrivov Ilya V.
Publication year - 2019
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201900736
Subject(s) - terahertz radiation , resonator , metamaterial , optics , materials science , wavefront , capacitive sensing , optoelectronics , lithography , capacitor , physics , computer science , quantum mechanics , voltage , operating system
Metasurfaces offer a highly flexible platform for controlling the propagation and localization of electromagnetic waves. Due to the relatively large size of commonly used resonators, various undesirable effects including spatial dispersion and spurious diffraction occur, thus limiting the metasurface performance. To overcome these problems, one straightforward approach is to utilize deeply subwavelength metaunits. In contrast to conventional approaches that minimize the resonator size by reshaping the metallic patches, the capacitive gaps are reshaped, an approach which is more robust to material loss, minimizing the problem of overdamping. As an example, a novel design based on interdigital capacitors (meander gap) is introduced with extremely subwavelength gaps for use in the terahertz frequency range. The size of the new resonator can be reduced to below λ/30 in a reflective‐type terahertz metasurface, while maintaining the 2 π phase shift required for full wavefront control. Using an advanced electron‐beam lithography technique, a proof‐of‐concept experiment is performed and a 5 mm × 5 mm beam deflector is fabricated, with the capacitive gaps as small as 300 nm (≈λ/1130). The device performance is characterized using angle‐resolved time‐domain spectroscopy. The study provides useful insight for ultracompact metadevices based on deeply subwavelength metaunits working at terahertz frequencies and beyond.